I just cannot figure where to put it! It is maybe a full page or a little more of text describing the basics of my system, to open a discussion on it. I don't feel to expose the points 1 by 1 because it is hard to understand one thing isolated from the ensemble. First thoughts is for precise questions about one aspect of a system and playtest is about playtest.... I can't figure a correct place to post it!

What should I do? Maybe It is just not the place! should I go to less serious websites?

You're being too specific about First Thoughts. You should use that forum for what you're talking about. If anyone specifically told you that First Thoughts is only for particular bits and pieces of a game, then (a) they were grossly wrong and (b) please send me a private message pointing to that thread or otherwise giving me the details.

Ron, I think the advice I've seen given to the OP on this subject is essentially in line with the forum rules:

"This forum is for working through early drafts and posing design questions about the fundamental concepts for new games. If you're starting a thread here, then it's very important for you to make specific inquiries and to raise specific points - don't post a ton of material and ask "what do you think," because it won't help much."

As I just told In the new post on AethEra's system on first thoughts, I don't think it is still relevant to read the entire 3 sessions of playtest. Maybe just in diagonal, knowing that most of the system changed after and because of these playtests!

The description of the setting on the top is still relevant though. For a more accurate idea of what the mechanic look like now, see the System in first thoughts,

Once you start playtesting a game, do not post again about it in First Thoughts. First Thoughts is a kiddie pool. After you playtest a game even once, all other posting about it goes into Playtesting.

Yes - even if the new thread does not actually describe a playtesting sesion. That doesn't matter. The new thread can be anything at all about your game in development. But it'll go in the Playtesting forum from that point on.

I am very busy with GenCon prep so I have not been able to monitor the situation in First Thoughts very well lately. I will return there and start moving some threads which need to go into Playtesting, as soon as I can.